Model of the Origin of the Solar System

What is a model? A model is a like a theory, but more specific. A theory is a general idea about how nature works, whereas a model represents a specific event or object. Eg. Theory of evolution vs Model of the atom

What makes a good model? explains previous observations simple makes predictions that, when checked, turn out to be true

A model of how of solar system began should explain... The motion of the planets and satellites. The position and size of each of the planets. The characteristics of the planets. The composition and size of the sun.

Orion Nebula

NEBULA: A large ball of dust and gas.

From our knowledge of gravity, all the mass in the nebula will be pulled in toward the centre. But this would explain only the presence of the sun!

One way that this wouldn’t happen is if the nebula is rotating.

But this alone would not explain the presence of so many planets. For that, we need to assume that there was not uniform density at the beginning.

Omega Nebula

As gravity forces the majority of the mass toward the centre, the nebula spins faster. The rest of the nebula will flatten out.

Most of the mass is concentrated near the center of the spinning disk.

Gravity pulls in matter to form rings in regions of locally higher density.

Those matter in the rings, in turn, clump together as they collide.

Eventually the gravity pulls the mass into a spherical shape we now call planets.